An autonomous system (AS) includes routers typically owned and/or otherwise controlled by an independent organization, such as businesses, government entities, and/or corporations. An AS of a first entity may be communicatively linked with the AS of one or more other entities. However, each organization may exhibit exclusive control over its respective autonomous system(s) (ASes), which allows an administrator of the AS to control the manner in which the AS is operated. The AS may be configured by the administrator to permit network traffic related to the organization while blocking more generalized Internet traffic. In the event that the organization has two or more ASes, each AS must run a common exterior routing protocol even if the internal routing protocol(s) of each AS are different and/or otherwise unique.
A border gateway protocol (BGP) is the common exterior routing protocol that is employed to allow two or more ASes to communicate with each other. The BGP allows one or more separate networks, such as ASes, to select communication routes between hosts. The communication routes are typically stored in routing tables of BGP routers. The routing tables allow the BGP routers of different networks (for example, alternate ASes) to exchange reachability information. Route information is exchanged between the BGP routers and propagated throughout the network(s) that ultimately allow ASes to determine communication paths to each other.
To ensure that BGP routers are available as one or more of the communication routes for a host, the BGP routers establish sessions, provide Keepalive notification messages, and exchange routing update information to identify new routing opportunities and/or to remove routing paths that are no longer functional. When a BGP session established by a BGP router fails, then one or more BGP router neighbors typically purge their routing tables of the information related to the BGP router associated with the failed BGP session. However, BGP router sessions may sometimes fail in an infrequent manner and the session may re-establish a short time after failure. Such intermittent failure may be tolerated by the administrator and/or the organization that employs the administrator (for example, an Internet Service Provider). In other circumstances, the failure and re-establishment of the BGP session may occur with greater frequency, which may be problematic for customers of the administrator.